The neuronal correlates of mirror therapy: an fMRI study on mirror induced visual illusions in stroke patients
Résumé
To investigate the neuronal basis for the effects of mirror therapy in stroke patients. Twenty-two stroke patients participated in this study. We used functional magnetic resonance imaging to investigate neuronal activation patterns in two experiments. In the unimanual experiment, patients moved their unaffected hand, either while observing it directly (no-mirror condition), or while observing its mirror reflection (mirror condition). In the bimanual experiment, patients moved both hands, either while observing the affected hand directly (no-mirror condition) or while observing the mirror reflection of the unaffected hand in place of the affected hand (mirror condition). A two-factorial analysis with movement (activity versus rest) and mirror (mirror versus no-mirror) as main factors was performed to asses neuronal activity resultant of the mirror illusion. Data of 18 participants were suitable for analysis. Results showed a significant interaction effect of movement x mirror during the bimanual experiment. Activated regions were the precuneus and the posterior cingulate cortex (p<0.05 FDR). In this first study on the neuronal correlates of the mirror illusion in stroke patients we showed that during bimanual movement the mirror illusion increases activity in the precuneus and the posterior cingulate cortex, areas associated with awareness of the self and spatial attention. By increasing awareness of the affected limb the mirror illusion might reduce learned non-use. The fact that we did not observe mirror-related activity in areas of the motor or mirror neuron system questions popular theories that attribute the clinical effects of mirror therapy to these systems.
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